(1) Field of the Invention
The present invention relates to a transmission apparatus and a data communication channel processing method and, for example, to a transmission apparatus and a data communication channel processing method suitable to use for management (monitoring, control) of a network conforming to the SONET (Synchronous Optical Network) or the SDH (Synchronous Digital Hierarchy) system.
(2) Description of Related Art
At present, as a user network interface for realizing B-ISDN (Broadband aspects of Integrated Services Digital Network), SDH (Synchronous Digital Hierarchy) [referred to as SONET (Synchronous Optical Network) in North America] is standardized as an international standard for the purpose to integrate the already existing digital hierarchy in each country of the world.
Then, an example of the SONET/SDH network configuration is a network configuration comprising a data communication network (DCN:Data Communication Network) for transmitting data for monitoring and controlling a transmission apparatus (NE: Network Element), which is a component in the network, independently of a network for transmitting main signals.
In such a network, a monitoring and controlling terminal that functions as an NMS (Network Management System) for a SONET/SDH network communicates with an NE constituting the SONET/SDH network via the DCN and transmits and receives monitoring and controlling information for performing an NE control and a line control by, for example, an OSI (Open System Interconnection) packet, thereby performing monitoring and control of the NE constituting the SONET/SDH network (for example, operation setting of each NE and a line control when an alarm signal is detected).
By the way, the DCN is constructed so as to have a data communication channel (DCC: Data Communication Channel) terminated between NEs and an NE that generates and terminates the DCC and terminates a monitoring and controlling packet (OSI packet) included in the DCC, and further routes monitoring and controlling information between DCCs.
Further, the DCC transmits an OSI packet for monitoring and controlling the SONET/SDH network and the NE and an IP packet used for other purposes by using, for example, a part (for example, the three bytes in the third row shown by the diagonally shaded area in FIG. 9) of a section overhead (SOH) in a SONET overhead (Overhead Byte) on a main signal interface (main signal frame) shown in FIG. 9. For example, a TL1 message, an NE system software file and a database (DB) file, etc., are transmitted by the OSI packet.
Here, the SOH is information that is terminated both at a relay regeneration station (regenerator node) and at a terminal station (multiplexing/demultiplexing node) and in SONET, information that is also referred to as a line overhead (LOH) and terminated only at the terminal station is defined. For the LOH, a byte for the DCC is defined, however, the LOH is not used for the current network management because not terminated at a relay station.
As a form of a network that uses the above-described SONET/SDH (hereinafter, SDH is assumed to be included when indicated just as SONET), there is a network form, for example, as shown in FIG. 10.
The SONET/SDH network shown in FIG. 10 is configured so as to comprise a monitoring and controlling terminal (monitoring and controlling system) 101, SONET transmission apparatuses to be monitored and controlled, that is, level 2 (L2) SONET transmission apparatuses (SONET L2 NE) 300-M (simply referred to as “NE300” when a distinction is not made) and level 1 (L1) SONET transmission apparatuses (SONET L1 NE) 400-M-N (M=0, 1, 2, . . . , N=0, 1, 2, . . . ) (hereinafter, simply referred to as “NE400” when a distinction is not made) in one DCN 100 and these SONET transmission apparatuses 300 and 400 are managed (monitored and controlled) by the monitoring and controlling terminal 101 for each of areas 200-0 to 200-M (hereinafter, simply referred to as “area 200” when a distinction is not made).
In other words, the level 2 NE300-i (i=0 to M) and the level 1 NE400-i-j (j=1 to N) constitute one area 200-i (#i) to be monitored and controlled and the NE group to be monitored and controlled is set with the area 200 as a unit. Here, the L2 NE300 means an NE, which is a communication gateway across the areas 200, and L1 NE400 means an NE other than that.
Then, the monitoring and controlling terminal 101 as an NMS hierarchically manages the NE 300, which is a communication gateway across the areas 200, and the NE 400 provided under the control of the NE 300, thereby the DCN 100 can be managed hierarchically for each area 200. Here, which of the areas 200 the NE 300 and NE 400 belong to is determined by, for example, a predetermined parameter set to the NE and the information (area attribute) can also be set by the DCC.
Now, all of the NEs (NE 300 and NE 400) existing in the DCN 100 manage the address information about all of the NEs within the capacity of a memory for managing address information and enable routing of the monitoring and controlling information among all of the NEs. Here, the memory for managing address information is provided to each NE (NE 300 and NE 400) and stores the address information, a routing table, etc.
In one DCN 100, up to M+1 (for example, 250) areas 200 can be managed and in each area 200, up to N+1 (for example, 300) units including the NE 300 and the NE 400 can be managed.
By such a hierarchical network management method, the NE 400 can manage as much information as necessary for the routing of the monitoring and controlling information (OSI packet) in the area 200 and the NE 300 can manage as much information as necessary for the routing within the local area 200 and between the areas 200, thereby it is made possible to transmit and receive the monitoring and controlling information among all of the NEs in the DCN 100.
By the way, the number of manageable areas (manageable upper limit area number: M+1) in one DCN 100 described above and the number of manageable NEs (manageable upper limit NE number: N+1) in one area 200 is limited by the memory size of the memory for managing address information provided in the NE and the search rate of the routing information, and in the most recent NE, for example, M+1=250 and N+1=300, approximately. This means that the NE 300 can manage up to 250 pieces of address information and the NE 400 can manage up to 300 pieces of address information of the NE in the area 200.
In other words, by using the hierarchical network management method as shown in FIG. 10, it is made possible to manage up to 300 (manageable upper limit NE number)×250 (manageable upper limit area number)=75000 NEs in one DCN 100 with the memory size of the memory for managing address information provided in the most recent SONET transmission apparatus.
Note that, in the patent document 1 to be described later, a label switching technology is disclosed, which combines an ATM switch and a data relay control device in order to transfer a large amount of data at high speed in an IP network, and cut-through transfer of data under specific conditions is also disclosed.
Further, in the patent document 2 to be described later, a control as to whether or not a packet is cut through based on mapping of the packet for considerably reducing routing processing in a packet transmission system is disclosed.
[Patent document 1] Japanese Patent Application Laid-Open No. 2000-92085
[Patent document 2] Japanese Patent Application Laid-Open No. 2000-244562
According to the technologies described above, in the most recent SONET transmission apparatus, up to 250 areas 200 can be managed in one DCN 100 and further by managing up to 300 NEs for each of the areas 200, up to 250×300=75000 NEs can be managed in one DCN 100, however, the hierarchical NE management with the presence of L1 and L2 NEs as shown in FIG. 10 is complex and not necessarily easy, therefore, some users may be reluctant to use and the number of NEs to be managed at the initial stage of the construction of a network is comparatively small, therefore, it is frequent that the NEs are managed only in the single area 200, not divided in the DCN 100 by the desire of a user.
In this case, up to N+1 (for example, 300 here) NEs can be managed in one DCN 100, however, when the number of NEs in the network increases by the coupling of a plurality of already existing networks, the expansion of a network, etc., there frequently occurs the case where the number of NEs in the DCN 100 exceeds the manageable upper limit NE number (here, N+1).
Here, the network state when the number of NEs in the DCN 100 exceeds the manageable upper limit NE number is explained by using FIG. 11.
For example, in a state in which the four NEs 400-0-0, 400-0-1, 400-0-2, and 400-0-3 constituting an already existing ring network (ring A) and the four NEs 400-0-4, 400-0-5, 400-0-6, and 400-0-7 constituting an already existing ring network (ring B) are managed as one area 200-0 by the monitoring and controlling system 101, as described above, each NE 400 manages address information of all the NEs 400 in the area 200-0 in a table.
Then, when a new NE 400-0-(N+1) is added in the area 200-0, the neighboring NEs 400-0-3 and 400-0-4 detect the addition of the NE 400-0-(N+1) and update the memory for managing address information (routing table) of the local station, and notify the other NEs 400 in the area 200-0 of the updated information. Due to this, the memory for managing address information of all the NEs 400 in the area 200-0 is updated.
When, however, a new NE 400-0-(N+1) is added in a state in which the number of NEs in the area 200-0 reaches the manageable upper limit NE number, it is not possible for each NE 400 in the area 200-0 to newly register the address information of the newly added NE 400-0-(N+1) to the memory for managing address information because of limitation of the memory size.
Therefore, it is not possible to communicate with the added NE 400-0-(N+1) and further, it is not possible to communicate with the NE 400-0-3 connected ahead of the NE 400-0-(N+1). As a result, a phenomenon occurs that monitoring and control of the NE 400 constituting the ring network A that is monitored and controlled hitherto cannot be performed any longer.
Further, when the already provided DCN 100 is constructed by one area 200-0, when the area management as shown in FIG. 10 is applied following an increase in the number of NEs, a review of the DCN architecture, an area resetting of the already provided NE, etc., are required, however, when such a setting is performed, communication via the NE 400 in question is disconnected in the meantime, therefore, monitoring and control of the NE 400 connected ahead of the NE 400 in question cannot be performed and there arises a problem that such a resetting cannot be performed for management.
Because of this, a method is demanded, which realizes addition of the NE 400 in the number exceeding the manageable upper limit NE number without the need to considerably modify the already provided network configuration (a configuration in which all of the NEs 400 present in a network are managed in one area 200-0).
The methods disclosed in the above-mentioned patent documents 1 and 2 are not aimed at the area management in the DCN 100, therefore, the above-mentioned problem cannot be solved.